WASHINGTON (AP) — The more Democrats learn about Bernie Sanders, the more they appear to like him.

A greater percentage of Democratic registered voters view the Vermont senator as likable, honest, competent and compassionate than they did just two months ago, according to a new Associated Press-GfK poll. Seventy-two percent now believe he could win the general election, a 21 percentage point increase from the last time the survey was conducted in December.

The findings underscore the challenge facing Hillary Clinton as she enters the Democratic contest’s pivotal spring stretch, when primaries across the country mean that many of the party’s voters will finally get their say on her candidacy.

Clinton’s campaign has argued that as voters learned more about his record, Sanders will begin to lose support. Instead, it seems that as Sanders has gotten more scrutiny, support for him has only grown. While Clinton continues to be the Democratic candidate who’s most well-liked within her own party, Sanders is gaining on her.

Woodrow Benford, 58, who lives outside Minneapolis, says he didn’t know much about Sanders before he announced his presidential bid, but now Benford plans to caucus for him on March 1.

“Some changes need to be made, some major changes — he’s addressing them,” he said. “I like Hillary Clinton; don’t get me wrong. But she’d never say she’s going to break up the big banks.”

Though Sanders is gaining ground with Democrat voters, Clinton maintains a commanding lock on the party’s leadership. An Associated Press survey of superdelegates, who are influential in picking the nominee, found that 449 of the party insiders back Clinton, while only 19 support Sanders.

If they continue to back Clinton overwhelmingly — they can change their minds— Sanders would have to win the remaining primary contests by a landslide to catch up.

Seventy-four percent of Democratic registered voters say they have a favorable view of Clinton, compared with 64 percent who say the same of Sanders. That’s a 10-point increase for Sanders from December, when 54 percent of Democratic registered voters held a favorable opinion of him.

But 16 percent of Democratic registered voters still say they don’t yet know enough about Sanders to form an opinion. “I know a lot of my Democratic friends are telling me, ‘Feel the Bern,’ but I can’t say that I like him or dislike him,” said Mona Lamberson, 59, of North Philadelphia. “He’s kind of new to the game.”

Since December, Sanders has gained on other measures, too. Six in 10 say he’s at least somewhat decisive, after half said so in the earlier poll. And 64 percent call him competent, after 55 percent said so in December.

Sanders is also more likely to be viewed as very or somewhat honest than he was in December, 64 percent to 56 percent. On that issue, he has a nine percentage point edge over Clinton, who’s viewed as honest by 55 percent of Democrats.

Sanders is the only candidate in either party who’s viewed as somewhat or very compassionate, honest and likable by at least half of all registered voters, and has a significant advantage over Clinton among all voters on each of those measures. Just 30 percent of all voters consider Clinton honest.

“I was going to bite my tongue and vote for Hillary, but I never really trusted her,” said Robert Stone, a 59-year-old from Hilton Head, South Carolina, who already cast an absentee ballot for Sanders. “Every time she opens her mouth, I can’t help but think she’s lying about something.”

But the poll also finds that Clinton maintains a variety of advantages over Sanders. Nine in 10 Democratic registered voters say they think she could win a general election, a 16-point margin over Sanders. She has a 13-point advantage on being viewed as at least somewhat decisive, and a 15-point advantage on being viewed as competent.

Democratic voters are slightly more likely to say that Clinton represents their positions on the issues very or somewhat well than say the same about Sanders, 73 percent to 63 percent. Minority and women voters appeared more likely to describe her as likable and inspiring.

“He’s a very nice boy, but I think it’s all pie in the sky, what he has to offer,” said Renee Gold, 83, of Sarasota, Florida. “Clinton is strong, I admire her and I think if she were to be elected, it would be a good presidency.”

Clinton and Sanders are each viewed positively by about 4 in 10 registered voters overall. But while all registered voters are about evenly divided in their opinions of Sanders, more than half have an unfavorable view of Clinton.

Still, 52 percent of registered voters say they would at least consider voting for each Democrat in a general election, putting them at least slightly higher than every Republican candidate but Marco Rubio on that measure.

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The AP-GfK Poll of 1,033 adults, including 389 Democratic or Democratic-leaning registered voters, was conducted online Feb. 11-15, using a sample drawn from GfK’s probability-based KnowledgePanel, which is designed to be representative of the U.S. population. The margin of sampling error for all respondents is plus or minus 3.4 percentage points, and is plus or minus 5.5 percentage points for Democratic voters.

Respondents were first selected randomly using telephone or mail survey methods, and later interviewed online. People selected for KnowledgePanel who didn’t otherwise have access to the Internet were provided access at no cost to them.